Well heads for oil and gas wells are often topped by a plurality of system components, such as blow out preventers, gauges, and valves atop the production casing. The combination of components mounted atop the well head is often referred to as a “Christmas tree”, or “tree” for short. The junction between the well head and the tree may be just above ground level, at ground level, or slightly below ground level.
Many of these connections and components may leak some oil, salt water, or often a combination of both. This leakage may drip, run or fall onto the ground surrounding the well head, causing environmental damage, danger to nearby wildlife and livestock, and hazards for the crew working on the well site. It is impractical to prevent all drips and leaks, especially on older wells which are subjected to a variety of corrosive forces as well as vibration from pump motors. So, many well are provided with containment cellars, which are generally lined pits formed around the well head with a sufficient diameter to catch the drips, runs and leaks. The containment cellars are often provided with a permeable bottom, such as gravel, 6′ to 10′ below ground level, which allows the leaking oil and salt water to seep back down into the ground, well below ground level, thereby preventing the environmental damage and hazards. The top of these containment cellars are often provided with a grate to prevent animals and crew members from falling into the pit, but through which the leaking liquids can readily pass.